The major objective of this project will be to systematically characterize the effects of different types (chrysotile, amosite and crocidolite) and sized (less than 5 Mum to 5 20 Mum in length) of asbestos fibers on normal and GCG-activated rabit alveolar macrophages using various physiologic parameters. These parameters will include viability, motility, enzyme release and various metabolic reactions. These metabolic reactions will include 02 uptake, HMS, H202 production, superoxide production, reduction of tetrazolium dye and hydroxyl radical production. In addition, a microscopic and ultramicroscopic study will be carried out to confirm phagocytosis of the small Asbestos particles as well as determine the configuration that macrophages take when they are unable to phagocytose large non-phagocytosable asbestos fibers. The working hypothesis is that asbestos fibers in the 5 to 20 Mum x 0.2 to 0.4 Mum can gain entrance to the alveolar ducts and alveoli and are then difficult to remove by alveolar macrophages. As a consequence, these fibers persist and accumulate. It is also proposed that small particles less than 5 Mum in length are phagocytosed by alveolar macrophages which can result in impaired mobility and a further perturbation of the alveolar and alveolar duct clearing mechanism which is almost solely dependent on alveolar macrophages.